Clutchmasters in the States sell Clutch kits for the ST170 (SVT overthere) and they are rated from stage 1-5 i think, mine is middle of the road kevlar type thats rated to take probably twice as much power as standard. The kit was £600ish and came with Uprated friction plate and uprated cover, Lightweight flywheel and brand new slave cylinder. Ford will want £120+ for the slave cylinder, up to and over £500 for the flywheel and £300+ for the clutch plus fitting.